Methods and apparatus for treating water and wastewater employing a cloth filter

ABSTRACT

A backwash header for a cloth filter includes a body having a length, a diameter, first and second ends, a longitudinal axis, and an exterior surface, the body defining at least one internal cavity. The body includes at least one suction slot sized to allow fluids and solids to enter the internal cavity from outside of the exterior surface. A structure is attached to a portion of the exterior surface of the body around and extending away from the suction slot to form an open-ended chamber defined by the structure and a portion of the exterior surface near the suction slot. The structure allows fluids and solids to enter the open-ended chamber and then the suction slot and cavity from a material being cleaned. Cloth filters and methods of treating water and wastewater using the backwash headers and cloth filters.

BACKGROUND INFORMATION

1. Technical Field

The present disclosure relates in general to the field of water and wastewater treatment.

2. Background Art

A cloth filter typically comprises a tank or vessel, which may be concrete, metal, fiberglass-reinforced plastic (FRP) or other material. A source of screened, secondary effluent flows into the unit from an influent trough, and filtered effluent leaves the unit through an effluent trough. Influent may traverse an influent weir, a scum or hydraulic optimization baffle, then approaches one or more filter cassettes. In currently known systems, each filter cassette may have at least one dedicated backwash vacuum shoe assembly positioned on one side of filter cloth fluidly attached to the central rotatable backwash conduit. In some other known embodiments the filter cassettes rotate during backwashing, while the backwash shoes remain stationary. One such backwash shoe is described in assignee's U.S. Pat. No. ______ (S 4046-US-NP).

As explained in the above patent, commonly used vacuum backwash shoes consist of using either a flat shoe having one or more suction orifices, or a shoe with lifts on the ends but still having a flat underside with a single slot/opening to sweep a single filter cloth clean. The limitations of these common backwash shoes were pointed out in the previous patent. In particular, in the older shoes the leading edge of the flat underside may compress, squeeze, and dislodge captured solids out of the reach of the suction of the backwash system; and even worse may force solids through the cloth to the filtered water side, thereby contaminating the filtered water. The flat underside may not provide for a volume of high turbulence that would enhance the cleaning/scouring effect by filtered water, and may not prevent “short-circuiting” of unfiltered secondary effluent into the shoe. It was also noted that backwash shoes that raise the shoe off the cloth surface inherently weaken the impact of the suction cleaning

The backwash shoes of the above-mentioned patent (as illustrated schematically in FIG. 1) improved upon the common backwash shoes by providing a hood attached to the exterior surface of the body of the backwash header around and extending away from the suction slot to form a chamber defined by the hood and a portion of the exterior surface near the slot. The chamber includes first and second sub-chambers on opposites sides of the slot, wherein the sub-chambers have sufficient volume to allow gradual straightening and relaxing of fibers of a filter material being cleaned by the backwash header. The first and second sub-chambers each comprise first and second cylindrical rods (122, 128) extending substantially parallel to the slot and attached to the tubular body, and third and fourth cylindrical rods (132, 134) extending substantially perpendicular to the slot and attached to the tubular body.

The backwash shoes of the above-mentioned patent and illustrated in FIG. 1 proved successful overcoming many of the faults of previous versions, however further improvement was desired.

There is a need in the cloth filter art for improved backwash mechanisms, and cloth filters and methods employing the improved backwash mechanisms in water and wastewater treatment facilities.

SUMMARY

Apparatus and methods of the present disclosure are improvements over those of the patent discussed above.

A first aspect of this disclosure is an apparatus comprising:

a body having a length, first and second ends, a longitudinal axis, and an exterior surface, the body defining at least one internal cavity;

the body comprising at least one slot sized to allow fluids and solids to enter the internal cavity from outside of the exterior surface; and

a structure attached to the exterior surface of the body proximate to and on opposite sides of the slot, the structure substantially parallel to and extending away from the slot to form an open-ended chamber, the open-ended chamber comprising first and second open-ended sub-chambers on opposites sides of the slot;

wherein the open-ended sub-chambers have sufficient volume to allow gradual straightening and relaxing of fibers of a filter material being cleaned by the apparatus, and allow relatively clean fluid to pass through the filter material in a reverse direction upon application of a suction pressure in the internal cavity, and allow the relatively clean fluid and solids previously adhered to the fibers to enter the open-ended chamber, then the slot and internal cavity while substantially preventing other relatively less clean fluids and solids from entering the open-ended chamber, slot and internal cavity.

A second aspect of this disclosure is a backwash header comprising:

a tubular body having an exterior surface, the tubular body defining at least one internal cavity;

the tubular body comprising at least one slot sized to allow fluids and solids to enter the internal cavity from outside of the exterior surface; and

a hood structure attached to a portion of the exterior surface of the body proximate to and on opposite sides of the slot, extending away from the suction slot to form an open-ended chamber, the open-ended chamber comprising first and second open-ended sub-chambers on opposites sides of the slot, wherein the open-ended sub-chambers have sufficient volume to allow gradual straightening and relaxing of fibers of a filter material being cleaned by the backwash header, and allow relatively clean fluid to pass through the filter material in a reverse direction upon application of a suction pressure in the internal cavity, and allow the relatively clean fluid and solids previously adhered to the fibers to enter the open-ended chamber, then the slot and internal cavity while substantially preventing other relatively less clean fluids and solids from entering the open-ended chamber, slot and cavity.

A third aspect of the disclosure is a backwash header comprising:

a tubular body having a length, first and second ends, a longitudinal axis, and an exterior surface, the tubular body defining at least one internal cavity;

the tubular body comprising first and second slots positioned on substantially opposite exterior surface portions of the tubular body, wherein each slot is substantially parallel to the longitudinal axis of the tubular body, each slot has a length that is less than the length of the tubular body, each slot positioned away from the first and second ends of the tubular body;

first and second hoods attached to separate portions of the exterior surface of the tubular body proximate to and extending away from the respective first and second slots to form first and second open-ended chambers defined by the respective hoods and portions of the exterior surface near respective slots, the first and second open-ended chambers each comprising first and second open-ended sub-chambers on opposites sides of each respective slot, wherein the first an second open-ended sub-chambers have sufficient volume to allow gradual straightening and relaxing of fibers of a filter material being cleaned by the apparatus and allow relatively clean fluid to pass through the filter material in a reverse direction upon application of a suction pressure in the internal cavity, and allow the relatively clean fluid and solids previously adhered to the fibers to enter the open-ended chambers, then the slots and then the internal cavity while substantially preventing other relatively less clean fluids and solids from entering the open-ended chambers, slots and internal cavity, the first and second open-ended sub-chambers each consisting of first and second cylindrical rods (preferably cylindrical, although other shapes are within the scope of the invention) extending substantially parallel to their respective slot and attached to the tubular body.

A fourth aspect of this disclosure is an apparatus for treating water or wastewater comprising:

a vessel having a floor and walls defining a cloth filter zone comprising one or more cloth filter cassettes positioned vertically therein, and one or more backwash headers positioned adjacent one main filter surface of at least one cloth filter cassette;

wherein the backwash header comprises a tubular body having a length, a diameter, first and second ends, a longitudinal axis, and an exterior surface, the tubular body defining at least one internal cavity;

the body comprising at least one suction slot sized to allow fluids and solids to enter the cavity from outside of the exterior surface, and

a hood structure attached to a portion of the exterior surface of the body proximate to and on opposite sides of the slot, extending away from the suction slot to form an open-ended chamber, the open-ended chamber comprising first and second open-ended sub-chambers on opposites sides of the slot, wherein the open-ended sub-chambers have sufficient volume to allow gradual straightening and relaxing of fibers of a filter material being cleaned by the backwash header, and allow relatively clean fluid to pass through the filter material in a reverse direction upon application of a suction pressure in the internal cavity, and allow the relatively clean fluid and solids previously adhered to the fibers to enter the open-ended chamber, then the slot and internal cavity while substantially preventing other relatively less clean fluids and solids from entering the open-ended chamber, slot and cavity, the first and second open-ended sub-chambers each consisting of first and second cylindrical rods (preferably cylindrical, although other shapes are within the scope of the invention) extending substantially parallel to their respective slot and attached to the tubular body.

A fifth aspect of this disclosure is a method of treating water or wastewater comprising:

flowing a suspended solids stream into a cloth filter vessel, the cloth filter vessel comprising a cloth filter zone comprising at least one cloth filter media cassette, producing a filter cake on external surfaces of the cloth filter media and a treated effluent stream from each cassette, and

backwashing (in certain embodiments periodically) the cloth filter media using a backwash header, the backwash header comprising:

a body having a length, first and second ends, a longitudinal axis, and an exterior surface, the body defining at least one internal cavity;

the body comprising at least one slot sized to allow fluids and solids to enter the internal cavity from outside of the exterior surface; and

a structure attached to the exterior surface of the body proximate to and on opposite sides of the slot, the structure substantially parallel to and extending away from the slot to form an open-ended chamber, the open-ended chamber comprising first and second open-ended sub-chambers on opposites sides of the slot, the first and second open-ended sub-chambers each consisting of first and second cylindrical rods (preferably cylindrical, although other shapes are within the scope of the invention) extending substantially parallel to their respective slot and attached to the tubular body;

wherein the open-ended sub-chambers have sufficient volume to allow gradual straightening and relaxing of fibers of a filter material being cleaned by the apparatus, and allow relatively clean fluid to pass through the filter material in a reverse direction upon application of a suction pressure in the internal cavity, and allow the relatively clean fluid and solids previously adhered to the fibers to enter the open-ended chamber, then the slot and internal cavity while substantially preventing other relatively less clean fluids and solids from entering the open-ended chamber, slot and internal cavity.

Further aspects and advantages of the disclosure will become apparent by reviewing the description of embodiments that follows.

BRIEF DESCRIPTION OF THE DRAWING

For a more complete understanding of the present disclosure, and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings, which are representative illustrations and not necessarily to scale, and in which:

FIG. 1 is a schematic perspective view illustrating one embodiment of a backwash header in accordance with the present disclosure;

FIG. 2 is a plan view of the backwash header embodiment of FIG. 1;

FIG. 3 is a side elevation view of the backwash header embodiment of FIG. 1;

FIG. 4 is a schematic cross-sectional view of the backwash header embodiment of FIG. 1 taken along section A-A of FIG. 3;

FIG. 5 is a schematic end elevation view of the backwash header embodiment of FIG. 1;

FIG. 6 is a schematic perspective view illustrating another embodiment of a backwash header in accordance with the present disclosure;

FIGS. 7A-C are a schematic cross-section views illustrating three backwash header embodiments cleaning a cloth of a cloth filter; and

FIG. 8 is a schematic side elevation view, and FIGS. 9 and 10 are schematic end elevation views illustrating a cloth filter embodiment in accordance with the present disclosure.

It is to be noted, however, that the appended drawings are not to scale and illustrate only typical embodiments of this disclosure, and are therefore not to be considered limiting of its scope, for the apparatus and methods of the disclosure may admit to other equally effective embodiments. Identical reference numerals are used throughout the several views for like or similar elements.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to provide an understanding of the disclosed backwash headers, cloth filters using same, and methods of their use. However, it will be understood by those skilled in the art that the backwash headers, cloth filters and methods may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible. All U.S. published patent applications and U.S. patents referenced herein, as well as any non-published U.S. patent applications and published non-patent literature are hereby explicitly incorporated herein by reference. In the event definitions of terms in the referenced patents and applications conflict with how those terms are defined in the present application, the definitions for those terms that are provided in the present application shall be deemed controlling.

Certain backwash header embodiments of the present disclosure may employ as the body a circular cross-section stainless steel pipe having diameter ranging from about 1-inch to about 6-inches in diameter that is slotted (one or more suction slots having slot width ranging from about 1/16-inch to about ¾-inch when the diameter of the tubular body is within the 2-6 inch range). In exemplary embodiments the backwash header has two suction slots positioned 180 degrees from each other. The backwash headers of the present disclosure, which may be described as “slotted pipe backwash headers”, may be sandwiched between surfaces of two filter cassettes so that a single backwash header can effectively clean two surfaces at a time. At a distance measured tangential to the pipe of approximately ¼-inch to 1 inch from the slot opening, on both sides of the slot openings, cylindrical rods, which may be stainless steel rods (⅛-inch to ½-inch diameter) may be welded or otherwise attached along the length of the slot. These cylindrical rods serve to form an effective seal, allowing relatively clean (filtered) fluid to be drawn through the filter cloth in “reverse direction” during backwashing and carry captured solids away from the filter cloth and into the chamber formed by the rods, into the slot, and into the internal cavity of the pipe, while substantially preventing “short-circuiting” of relatively unclean (unfiltered secondary effluent) form entering the backwash header slot during backwashing. In contrast to the backwash headers of U.S. Pat. No. ______, in all embodiments of the present disclosure there are no solid end rods (cylindrical or otherwise) at or near the ends of the slots connected perpendicularly to the ends of the cylindrical rods running the length of the slots. The inventor herein has surprisingly and unexpectedly found that those “end rods” were not necessary to effectively form a cleaning hood volume between the cloth surface and the backwash header. As used herein the term “open-ended chamber” means the chamber is open on its ends, either as illustrated further herein devoid of end rods, or with ends having holes or other passages therein. Importantly, the longitudinal rods may be set back from the slot to form first and second open-ended sub-chambers on opposites sides of the slot, wherein the open-ended sub-chambers have sufficient volume to allow gradual straightening and relaxing of fibers of a filter material being backwashed by the apparatus. In certain embodiments, this gradual straightening and relaxing may comprise an angular reversal of at least some of the fibers of the filter cloth during a backwashing operation, as further explained herein. The angular reversal of fibers may assist in releasing particles trapped in filter media.

Surprisingly, benefits of the backwash headers of the present disclosure are significant in number and degree of benefit, and perform as well as the backwash headers of U.S. Pat. No. ______. One benefit, already alluded to, is that they may be structured to clean two surfaces at a time versus the current shoes' ability to clean only one surface at a time. This feature may minimize the number of headers and complexity of filters employing them, thereby making cloth filters more cost-effective and easier to construct and maintain.

In certain embodiments, the cleaning hood formed by the structure attached to the exterior surface of the header produces open-ended sub-chambers having relatively less turbulent (in certain embodiments laminar) cleaning conditions on either side of the slot opening, and a relatively more turbulent region directly above the slot. The fibers of the filter cloth experience the first relatively less turbulent space, then a relatively more turbulent space, and then a second relatively less turbulent space, further enhancing the cleaning and scouring action of the backwash action, while not abruptly straightening or re-flattening the fibers of the filter cloth. The slot may then have a width that is smaller than the length of fibers in the filter material. In certain embodiments, this leads to another key benefit of the backwash cleaning headers described herein: the required backwash rate may be reduced from approximately 2.5 gallon per minute (gpm) per inch of slot length to approximately 0.5 gpm per inch of slot. This may significantly reduce the amount of backwash water (which has already been filtered by the cloth) that needs to be pumped back through the filter clot in the reverse direction, thereby proportionally reducing the energy costs for operation.

In yet other embodiments, the smooth (in some embodiments circular) shape of the structure extending away from the header body may minimize abrasion of the filter cloth, as there are no edges that would tend to abrade and wear the cloth. Furthermore, the ability to fabricate the headers of the present disclosure from readily available stainless steel materials/components in certain embodiments may make the backwash headers of the present disclosure more durable and cost-effective than shoes fabricated from plastic materials such as specially formed ultra-high molecular weight (UHMW) polyethylene or other non-metallic components, although these materials are not ruled out.

In certain apparatus embodiments, the slot may be generally parallel to the longitudinal axis of the body of the backwash header, and may have a slot length less than the length of the body.

In certain apparatus the structure may comprise a hood. In certain exemplary embodiments the body may be tubular, and the hood consists of first and second cylindrical rods extending substantially parallel to the slot and welded or otherwise attached to the tubular body.

In certain apparatus embodiments, the first and second cylindrical rods may each have a rod diameter such that the rod diameter is one quarter of the diameter of the tubular body or less. In certain other embodiments, the first and second cylindrical rods may each have a rod diameter such that the rod diameter is one eighth of the diameter of the tubular body or less.

Certain backwash header apparatus embodiments may have a single slot. In certain embodiments the slot may be substantially parallel to the longitudinal axis of the body of the backwash header. In certain exemplary embodiments the slot may have a length that is less than the length of the body. In certain embodiments, the slot may be positioned away from the first and second ends of the tubular body.

Certain other backwash header embodiments may comprise two slots positioned on substantially opposite exterior surface portions of the body, wherein each suction slot is substantially parallel to the longitudinal axis of the body. In certain of these embodiments, each slot may have a length that is less than the length of the body. In certain embodiments the lengths of the two slots may be substantially equal, although this is not a requirement. The slots may be positioned away from the first and second ends of the tubular body.

Certain backwash header embodiments may comprise first and second mounting brackets attached to the body. In certain embodiments the first and second mounting brackets may engage respective first and second tracks in a cloth filter apparatus.

Certain backwash header embodiments may comprise a flange connected to the first end of the body, the flange fluidly connected to a backwash suction pump of a cloth filter apparatus.

In certain backwash header embodiments the body may comprise a connection allowing the backwash header to be connected to an actuator mounted on a cloth filter apparatus.

In certain backwash header embodiments the body may be tubular having a cross-sectional shape selected from the group consisting of circular, oval, and polygonal.

Certain methods of treating water or wastewater may comprise methods wherein the cloth filter media is selected from the group consisting of needled nonwoven polyamide filter media, acrylic cloth, polyester cloth, nylon fibers, other carpet-like materials, and combinations thereof. In certain other methods the suspended solids stream may be a chemically-induced flocculated stream, wherein the flocculated stream percolates up through a sludge blanket comprising previously flocculated solids.

Certain other methods may comprise backwashing one or more of the cloth filters periodically using one or more rotating backwash headers. In certain other embodiments, one or more of the filter cassettes rotate on a central shaft while the backwash headers remain stationary during backwashing. In certain other embodiments, backwashing may be accomplished using cross-width backwash headers that traverse up and down, or side to side, or any angle to horizontal, and remove waste from substantially all of the surface area of the filter cloths. Yet other methods may comprise slideably moving one or more, or all, of the cloth filter cassettes vertically in vertical cassette guide members, allowing the cassettes to be moved vertically up and down adjacent one or more stationary backwash headers. As used herein, the term “adjacent” when discussing the relative positions of a backwash header and filtration material, includes both situations where the hoods of the backwash headers touch the filter material, and situations where there is no contact between the backwash headers and the filtration materials.

Certain exemplary methods may comprising moving the backwash header in a first direction across a surface of the cloth filter media during a first period of time, and reversing the direction of movement of the backwash header to move across the same surface of the cloth filter media during a second period of time. This may provide more thorough cleaning, while reducing wear of the cloth filter media.

Referring now to the drawing figures, FIG. 1 is a schematic perspective view of one embodiment 100 of a backwash header in accordance with the present disclosure, having a tubular body 102, a first end 104, a second end 106, and an exterior surface 108. Tubular body 102 defines at least one cavity 110, in this embodiment a single cavity 110, more clearly visible in FIG. 4. Although embodiment 100 comprises a tubular body that is substantially cylindrical (circular) in cross-section, “tubular” is not meant to be limited to cylindrical bodies. Tubular bodies having oval or polygonal (for example, rectangular and triangular) bodies may be envisioned and are considered within the present disclosure. Tubular body 102 may be steel, such as 304 or 316 stainless steel, titanium, aluminum, or other metal or metal alloy. In certain embodiments tubular body may be polymeric, such as a thermoplastic polymer, thermoplastic elastomer, or thermosetting polymer, or fiberglass reinforced plastic (FRP). If polymeric, the polymer may be filled or unfilled.

Again referring to FIG. 1, embodiment 100 includes a first suction slot 112 and a second suction slot 114 (not viewable in FIG. 1, but viewable in FIG. 4). Mounting brackets 116 and 118 are provided that allow mounting to a cloth filter system, not illustrated in FIG. 1. Mounting bracket 116 includes a extension 117 having a pair of holes 115 for screws, rivets, and the like. Similarly, mounting bracket 118 includes an extension 119 having a set of holes 121 for screws, rivets, and the like. Embodiment 100 also includes a flange 120 having four mounting holes 136, allowing flange 120 to be attached to a backwash suction pump, not illustrated. On the opposite end, mounting bracket 118 includes a vertical portion 123 that seals tubular body 102, for example by welding, although other sealing elements may be used, such as gasket arrangement, O-rings, and the like. Embodiment 100 also includes an actuator clevis bracket 126 that allows backwash header 100 to be attached to a backwash header actuator, not illustrated.

Embodiment 100 includes a pair of hoods 122 and 124, each hood consisting of first and second long cylindrical rods 128, 130. Cylindrical rods 128 and 130 are substantially parallel to a longitudinal axis “A” (FIG. 2) of tubular body 102. Cylindrical rods 128, 130 may be steel, such as 304 or 316 stainless steel, titanium, aluminum, or other metal or metal alloy. In certain embodiments they may be polymeric, such as thermoplastic elastomeric. In certain embodiments they are all the same material, but this is not required. If metallic, they may be welded, brazed, clipped, banded or otherwise attached to exterior surface 108 of tubular body 102. If polymeric, they may be attached using glue, plastic or rubber banding, clips or the like.

Referring now to FIGS. 2 and 3, FIG. 2 is a plan view of backwash header embodiment 100 of FIG. 1, and FIG. 3 is a side elevation view of backwash header embodiment 100 of FIG. 1. Tubular body 102 has a length “L”, while slots 112 and 114 each have a length L_(s) in this embodiment. The lengths of slots 112 and 114 are not necessarily equal in all embodiments. Tubular body 102 also has a diameter D in embodiment 100. Generally, the ratio of L to D may range from about 3:1 to about 100:1, or from about 5:1 to about 50:1, or from about 5:1 to about 10:1. The ratio of L to L_(s) may range from about 1:1 to about 10:1, or from about 2:1 to about 5:1. The diameter of cylindrical rods 128 and 130 may be ¼ or less of the diameter D of tubular body 102, or ⅛ or less than D.

FIG. 4 is a schematic cross-sectional view of backwash header embodiment 100 of FIGS. 1-3 taken along section A-A of FIG. 3. Apparent in this view of backwash header embodiment 100 are a pair of open-ended chambers 142 and 142A, each including a pair of open-ended sub-chambers 141, 143 on either side of slots 112, 114. Open-ended chamber 142 is formed by cylindrical rods 128, 130 and a portion of exterior surface of tubular body 102 between rods 130 and 128. Similarly, open-ended chamber 142A is formed by cylindrical rods 130A, 128A and a portion of exterior surface of tubular body 102 between rods 128A, 130A. Open-ended sub-chambers 141, 143 are the sub-chambers of random, high turbulence cleaning on either side of slots 112, 114, discussed earlier herein, that further enhance the cleaning and scouring action of the backwash action, while not abruptly straightening or re-flattening the fibers of the filter cloth. In embodiment 100, cylindrical rods 128, 130 are positioned proximate to slot 112, that is a distance “d” measured tangential to the pipe of approximately ¼-inch to 1 inch from each slot 112, 114, on both sides of each slot. Cylindrical rods 128, 130 may be stainless steel rods having diameter ranging from about ⅛-inch to about ½-inch, and may be welded or otherwise attached along the length of the slots.

FIG. 5 is a schematic end elevation view of backwash header embodiment 100 of FIG. 1, partially in phantom illustrating schematically the position of holes 136 in flange 120 in this embodiment. Angle α may range from about 20 to about 50 degrees, and in embodiment 100 is 45 degrees.

FIG. 6 is a schematic perspective view of another embodiment 200 of a backwash header in accordance with the present disclosure. Backwash header 200 differs from embodiment 100 of FIGS. 1-5 in that embodiment 200 only features one suction slot 112. As illustrated in FIG. 8, backwash headers 200 may be positioned to clean the outer cloth surfaces of the outer most filter cassettes, while backwash header embodiment 100 may be used between adjacent cassettes.

Referring now to FIG. 7, FIGS. 7A-C are schematic cross-sectional views of three different backwash header embodiments 100, 300, and 400 cleaning a filter cloth “FC” of a cloth filter. Filter cloth FC comprises a filter cloth backing FB and a plurality of fibers F having length L_(f). In all three embodiments, the backwash header is moving upwards, in the direction of the arrow, it being understood that the backwash headers could move in the opposite direction; or filter cloth FC could move while the backwash header is stationary, or both the backwash header and filter cloth FC could move in opposite directions. It is also understood that backwash headers may move first in one direction and then in the opposite direction in random or non-random time periods over substantially the same area of filter cloth FC. Longitudinal cylindrical rods 128, 130 and open-ended sub-chambers 141, 143 play a significant role in backwash header embodiments of this disclosure such as embodiments 100, 200, 300, and 400 inasmuch as open-ended sub-chambers 141 and 143 (FIG. 7A), open-ended sub-chambers 141A, 143A (FIG. 7B), and open-ended sub-chambers 141B, 143B (FIG. 7C) function to provide regions or spaces of transition allowing fibers F to remain partially erect and/or non-flattened against filter cloth backing FB in those regions or spaces. This allows slot width W to be less than the fiber length L_(f), and allows less backwash fluid to be used relative to systems with slot widths greater than the fiber length L_(f). Due to the combined movement of the header and the smooth geometry of cylindrical rods 128, 130, dislodged solids may be effectively removed via backwash fluid BW flowing in reverse direction (opposite normal filtration flow direction) through filter cloth backing FB, fibers F attached to backing FB near slot 112, then through slot 112, and into internal cavity 110. The smooth circular shape of compression rods 128, 130 may minimize abrasion of filter cloth FC, as there are no edges that would tend to abrade and wear cloth FC. Open-ended sub-chambers 141, 143 which are formed by compression rods 128, 130, and portions of the external surface of header body 102, produce a volume of high turbulence around slot opening 112 (and 114 when using embodiment 100), further enhancing the cleaning and scouring action of the backwash, and gradually opens and straightens the cloth fibers F in the vicinity of slot 112. In certain embodiments, where the fibers F normally extend away from filter cloth backing FB such as illustrated in embodiment 100, this gradual straightening and relaxing may comprise an angular reversal of at least some of the fibers F of the filter cloth during a backwashing operation. As illustrated in FIG. 7A, fibers in open-ended sub-chamber 141 that are behind rod 130 are generally angled downward toward slot 112, while these fibers will be experience a reversal or waving action as they approach rod 128 in open-ended sub-chamber 143. The gradual straightening, angular reversal or waving action of the fibers may also allow smaller width and more powerful cleaning slots to be used in apparatus of the present disclosure. Surprisingly, and unexpectedly, the absence of end rods allows the backwash headers to perform close to or as well or better than backwash headers have the end rods, with less cost and fabrication time and effort.

Backwash header embodiments 300 and 400 illustrated schematically in FIGS. 7B and 7C, respectively, are similar to embodiment 100 illustrated schematically in FIG. 7A, except that backwash header embodiment 300 has a rectangular-shaped cross-section body 102A, while backwash header embodiment 400 has a trapezoidal-shaped cross-section body 102B. A further difference in embodiment 300 is provisional of non-circular cross-section hood elements 328, 330, causing slightly different shaped open-ended sub-chambers 141A, 143A.

Embodiment 100 as illustrated schematically in FIG. 7A also illustrates welds 15, one way of attaching cylindrical rods 128, 130 to body 102. Other attachment mechanisms may be envisioned, such as brazing, soldering, use of adhesives, clips, bands, snaps, and the like.

In certain embodiments, another key benefit of backwash cleaning headers of the present disclosure is that the required backwash rate may be reduced from approximately 2.5 gpm per inch of slot length L_(s) to approximately 0.75 gpm per inch of slot length L_(s). This may significantly reduce the amount of backwash water that needs to be pumped, thereby proportionally reducing the energy costs for operation.

Referring now to FIGS. 8-10, FIG. 8 is a schematic side elevation view, and FIGS. 9 and 10 are schematic end elevation views of a cloth filter embodiment 500 in accordance with the present disclosure. Embodiment 500 employs a cloth filter having four filter cassettes 12 in a cloth filter zone 160, as described in assignee's U.S. Pat. No. 8,778,174. Embodiment 500 includes an influent conduit 202, in this embodiment retrofitted into an existing influent trough 4, but this is not necessary in new installations. Embodiment 500 may include features such as an influent screen and V-notch weir, neither of which is illustrated, which direct influent through a conduit 202 and valve V6 to influent distribution headers 204, 206 (only 204 is visible in FIG. 8) positioned just above the floor of vessel 2. Influent distribution headers 204, 206 are, in embodiment 500 generally positioned parallel to the side walls of vessel 2, but this is merely one possible arrangement. For example, another possible arrangement would be to have “T” or “X” shaped headers. In any case, headers 204, 206 each have a plurality of outlet holes or apertures 208 which allow influent to flow out of distribution headers 204, 206. Water level 152 in vessel 2 may be monitored and controlled by initiating backwashing using any well-known backwash assembly. Flocculated solids 240 and smaller solids are routed to the cloth 16 of filter cassettes 12. One or more valves (not illustrated) may be used to throttle or completely shut off flow of influent to distribution headers 204, 206. They may also be automatic flow-controlled valves, communicating with a PLC or other type of automatic controller to control level 152 according to a setpoint level and/or setpoint flow rate. Cleaned effluent fluid flows out of the filter through one or more effluent conduits 28, which may be manifolded together.

Referring again to FIG. 8, backwash headers 100 and 200 are fluidly connected to one or more backwash collection headers 312 via one or more flexible conduits 316. Backwash flow may be controlled via one or more valves 314. In embodiment 500, cross-width backwash headers 100 and 200 are moved by a drive assembly comprising supports 350, 352 (there are only two visible in each of the various views, but four total in embodiment 500), corresponding cylinders 354, 356 (a total of four, only two of which are visible in embodiment 500), and corresponding telescoping tie-rods 358, 360 (a total of four, only two of which are visible in embodiment 500). FIGS. 9 and 10 illustrate support 351, cylinder 355, and its corresponding telescoping tie-rod 359. Cylinders 354, 356 are actuated (electronically, pneumatically, or hydraulically) to force corresponding telescoping tie-rods 358, 360 to move upwards or downwards in telescoping fashion. Tie-rods 358, 360 are connected to support arms 362, 364, which in turn are connected to cross-width backwash headers 100 and 200, as illustrated. Support arms 362, 364 and backwash headers 100 and 200 form a backwash assembly. The entire backwash assembly, including backwash headers 100 and 200, are raised or lowered to wash all sides of filter cassettes 12 simultaneously. For example, in embodiment 500 of FIGS. 8-10, four filter cassettes having a total of eight filter surfaces to be cleaned would require three backwash headers of embodiment 100, and two backwash headers of embodiment 200. FIG. 9 illustrates the position of backwash header 200 at or near the beginning of a cleaning cycle, while FIG. 10 shows backwash header 200 near the end of a cleaning cycle.

As an alternative to the drive mechanism described in relation to FIGS. 8-10, the backwash headers may be driven by a drive assembly comprising a drive frame weldment which supports a drive motor, a drive shaft, a miter gear box, lifting screw jacks, and ancillary mechanisms (such as vertical backwash header guide members) to impart the vertical cleaning (backwash) motion. Other header drive mechanisms are described in assignee's U.S. Pat. No. 8,778,174.

In certain embodiments, when filtration headloss reaches a filtration termination set point, a backwash flow control valve may open. Then the backwash headers move vertically, sweeping the filter cloth surface from the bottom to top (or alternatively from top to bottom, or periodically switching directions). Also as described in U.S. Pat. No. 8,778,174, the backwash header travel stop may be controlled by a proximity switch, for example an infrared proximity switch, or other acceptable motion controller. Certain embodiments may comprise a backwash pump fluidly connected to the backwash header. In certain embodiments, the backwash pump is not required. Backwash driving head could simply be the level difference between the filtration termination set level and the backwash header discharge level, thereby eliminating the need for the backwash pump. It will be understood by those skilled in the art that cloth filters may comprise other various features, such as described in assignee's U.S. Pat. No. 8,778,174, and the embodiments described in this disclosure and that patent may be combined in certain other embodiments, and with other features that are not described herein but are normally associated with cloth filters.

Cloth filters are sized on the basis of “hydraulic loading rate”, and 3 to 6 gallons/day/ft² (gpd/ft²) is typical for design average flow rates of prior art cloth filters. For flocked phosphorous solids removal, however, prior art cloth filter surface overflow rates typically only range from about 2 to about 4 gpd/ft². Apparatus of the present disclosure may achieve, in some embodiments, from about 3 to about 6 gpd/ft² even for flocked phosphorous solids removal, which is a 50 percent or 100 percent increase of surface overflow rate over prior art cloth filters treating phosphorous-based solids. The modified cloth filters of this disclosure may be part of a packaged water or wastewater treatment plant.

Filter cloth media useful in the various embodiments of this disclosure may, in certain embodiments, be able to filter out solids having particles sizes of 10 microns or larger, or 5 microns and larger, and withstand washing or mechanical abrasion enough to remove retained materials, and may be characterized as organic polymeric filter cloth media or inorganic filter cloth media depending on the material performing the separation function. A single cassette of a cloth filter may have a filter area ranging from 1 to about 200 ft², or from 1 to about 50 ft², or from 1 to about 20 ft², and there may be upwards of 10 filter cassettes in a single filtration vessel. The filter area is dictated largely by the filtration task at hand, size of the vessel and influent solids loading and flow rate, and the like. It is understood that an organic filter cloth media might comprise inorganic materials, and vice versa.

Suitable cloth filter media may be woven or nonwoven, and may comprise one layer or may be multi-layered. The material selected for the filter cloth media should have numerous attributes that render the filter cloth media suitable for filtration service, such as structural integrity to withstand the pressure gradients of filtration and backflushing, and chemical resistance to attack or dissolution by the filtered species, filtrate, and chemical cleaning solutions such as chlorine, citric acid, sodium hydroxide, and other chemicals designed to minimize organic and inorganic fouling of the filter cloth media. The material should also have the ability to be fabricated readily into the preselected filter cloth media shape for a particular application. One useful cloth filter material is a nonwoven, needlefelted nylon (polyamide) fiber-based material. The same material in “pile” form is another suitable filter material. “Pile” and “needlefelting”, and “needling” are terms of art in the manufacture of nonwovens, and are readily understood by those skilled in the nonwovens art. Piled materials may also be needlefelted. Additional design criteria and considerations in the fabrication and selection of cloth filter media are disclosed in Purchas and Sutherland, “Handbook of Filter Media”, Elsevier Science Ltd. (2002), which is incorporated herein by reference, and especially Chapters 2 and 3 entitled “Woven Fabric Media” and “Nonwoven Fabric Media”, respectively. Patents describing piled and/or needled nonwovens include U.S. Pat. Nos. 3,673,048 and 3,755,055, both incorporated herein by reference. In certain embodiments, the filter material may comprise membrane materials or fine screened mesh (such as stainless steel screen mesh).

Pumps described in the various embodiments may be submersed in the liquid in vessel 2, or they may be positioned outside of the vessel 2. Cloth filter apparatus and methods of this disclosure may also include, or be fluidly connected with a chemical addition system, which may include mixers, pumps, tanks for flocculating chemical and other chemicals, which may be polymeric, flow meters, and the like. Cloth filter apparatus and methods of the present disclosure may include various sampling and viewing ports, as well as physical, chemical and biological property measurement devices, such as temperature, pressure, turbidity, flow rate (mass and/or volume), color, composition, particle size, and the like. The details of these sub-systems are readily understood by those skilled in the water and wastewater treatment art, and require no further explanation herein. It is also very common today to include data logging systems, such as one or more PCs and/or server computers running data acquisition software which may be accessed onsite or remotely.

In operation, modified cloth filters of the present disclosure operate as follows. Flow enters the filter through an influent conduit as described in FIGS. 8-10 and through one or more influent distribution headers near the bottom of the cloth filter vessel. At steady state, the influent moves up into the cloth filter zone and completely surrounds the cassettes and cloth filter media. As the flow passes through the cloth filter media, any remaining suspended solids are removed. The operator monitors the operation to view the filtered effluent of each filter cassette through the individual discharge ports. As solids accumulate on the cloth filter media, the flow through the media becomes restricted and the level of liquid in the vessel rises. The backwash process is triggered when the level reaches a pre-determined point or after a set time period. The outside-to-inside flow ensures that solids stay trapped within the vessel. In some embodiments, at least some of the backwash headers rotate across the surfaces of the filter media, removing captured solids from the media. In certain embodiments, the backwash headers rotate clockwise 360 degrees and then return counter-clockwise in sequence for efficient media cleaning, but this is not strictly necessary. The fixed-media design may incorporate one or more fixed media cassettes with rotating suction backwash headers that do not touch the cloth media, thus extending the life of the media. In embodiments such as embodiment 500 illustrated in FIGS. 8-10, backwash headers move upwards or downwards, or reciprocate upwards and downwards as desired. In embodiment 500 and similar embodiments, there is no need to drain the tank when replacing cassettes, saving water treatment facilities time and money. In certain embodiments, each cassette may be monitored separately, so effluent performance may be easily verified and segments requiring service are easily identified.

Cloth filters described herein may be used in biological treatment systems, for example, but not limited to, activated sludge systems, such as conventional activated sludge, extended aeration, complete mix activated sludge, continuous flow activated sludge, various batch reactor activated sludge systems, integrated fixed-film activated sludge (IFAS) and submerged fixed film (SFF) systems, and the like. They may also be used in non-biological systems, for example, but not limited to, metal precipitation, surface water treatment, cooling tower blow down treatment, and the like.

Backwash headers described herein and their equivalents can be retrofitted in existing cloth filters, or installed as new equipment in new cloth filters. Cloth filters of this disclosure can be retrofitted to existing concrete basins or sold as complete stand-alone filtration units. The units are user-friendly, high performance tertiary filters, suitable for both small and large flow applications, that remove suspended solids as small as 10 microns or less in certain embodiments, suitable for use in water and wastewater plants that have stringent suspended solids discharge permit requirements, phosphorous limits or require re-use quality effluent.

The various advantages of the described backwash headers and filter cloth media module configurations and modes will be readily understood by those of ordinary skill in the art upon reading this disclosure. Selection of backwash header and filter cloth media module configuration and mode of operation typically devolves to choosing those which provide maximum advantage and least disadvantage for a specific separation to be effected. It is believed the backwash headers described herein, and cloth filters employing them, will provide many advantages.

Although the foregoing examples and description are intended to be representative of the disclosure, they are not intended to in any way limit the scope of the appended claims. 

What is claimed is:
 1. An apparatus comprising: a body having a length, first and second ends, a longitudinal axis, and an exterior surface, the body defining at least one internal cavity; the body comprising at least one slot sized to allow fluids and solids to enter the internal cavity from outside of the exterior surface; and a structure attached to the exterior surface of the body proximate to and on opposite sides of the slot, the structure substantially parallel to and extending away from the slot to form an open-ended chamber, the open-ended chamber comprising first and second open-ended sub-chambers on opposites sides of the slot; wherein the open-ended sub-chambers have sufficient volume to allow gradual straightening and relaxing of fibers of a filter material being cleaned by the apparatus, and allow relatively clean fluid to pass through the filter material in a reverse direction upon application of a suction pressure in the internal cavity, and allow the relatively clean fluid and solids previously adhered to the fibers to enter the open-ended chamber, then the slot and internal cavity while substantially preventing other relatively less clean fluids and solids from entering the open-ended chamber, slot and internal cavity.
 2. The apparatus of claim 1, wherein the slot is generally parallel to the longitudinal axis of the body.
 3. The apparatus of claim 1, wherein the slot has a slot length less than the length of the body.
 4. The apparatus of claim 1 wherein the structure comprises a hood.
 5. The apparatus of claim 4 wherein the body is tubular, and the hood consists of first and second cylindrical rods extending substantially parallel to the slot and attached to the tubular body.
 6. The apparatus of claim 5 wherein the first and second cylindrical rods each have a rod diameter and the tubular body has a diameter such that the rod diameter is one quarter of the diameter of the tubular body or less.
 7. The apparatus of claim 5 wherein the first and second cylindrical rods each have a rod diameter such that the rod diameter is one eighth of the diameter of the tubular body or less.
 8. The apparatus of claim 1 comprising a single slot.
 9. The apparatus of claim 8 wherein the slot is substantially parallel to the longitudinal axis of the body and has a rectangular shape.
 10. The apparatus of claim 9 wherein the slot has a length that is less than the length of the body.
 11. The apparatus of claim 10 wherein the slot is positioned away from the first and second ends of the body.
 12. The apparatus of claim 1 comprising two slots positioned on substantially opposite exterior surface portions of the body, wherein each slot is substantially parallel to the longitudinal axis of the body, each slot has a length that is less than the length of the body, the lengths of the two slots being substantially equal, the slots positioned away from the first and second ends of the body.
 13. The apparatus of claim 1 comprising first and second mounting brackets attached to the body.
 14. The apparatus of claim 13 comprising a flange connected to the first end of the body, the flange fluidly connected to a backwash suction pump of a filter apparatus.
 15. The apparatus of claim 14 wherein the first and second mounting brackets engage respective first and second tracks in the filter apparatus.
 16. The apparatus of claim 15 wherein the body comprises a connection allowing the apparatus to be connected to an actuator mounted on the filter apparatus.
 17. The apparatus of claim 1 wherein the body is tubular having a cross-section selected from the group consisting of circular, oval, and polygonal.
 18. The apparatus of claim 1 wherein the slot has a width that is smaller than the length of fibers in the filter material.
 19. A backwash header comprising: a tubular body having an exterior surface, the tubular body defining at least one internal cavity; the tubular body comprising at least one slot sized to allow fluids and solids to enter the internal cavity from outside of the exterior surface; and a hood structure attached to a portion of the exterior surface of the body proximate to and on opposite sides of the slot, extending away from the suction slot to form an open-ended chamber, the open-ended chamber comprising first and second open-ended sub-chambers on opposites sides of the slot, wherein the open-ended sub-chambers have sufficient volume to allow gradual straightening and relaxing of fibers of a filter material being cleaned by the backwash header, and allow relatively clean fluid to pass through the filter material in a reverse direction upon application of a suction pressure in the internal cavity, and allow the relatively clean fluid and solids previously adhered to the fibers to enter the open-ended chamber, then the slot and internal cavity while substantially preventing other relatively less clean fluids and solids from entering the open-ended chamber, slot and cavity.
 20. A backwash header comprising: a tubular body having a length, first and second ends, a longitudinal axis, and an exterior surface, the tubular body defining at least one internal cavity; the tubular body comprising first and second slots positioned on substantially opposite exterior surface portions of the tubular body, wherein each slot is substantially parallel to the longitudinal axis of the tubular body, each slot has a length that is less than the length of the tubular body, each slot positioned away from the first and second ends of the tubular body; first and second hoods attached to separate portions of the exterior surface of the tubular body proximate to and extending away from the respective first and second slots to form first and second open-ended chambers defined by the respective hoods and portions of the exterior surface near respective slots, the first and second open-ended chambers each comprising first and second open-ended sub-chambers on opposites sides of each respective slot, wherein the open-ended sub-chambers have sufficient volume to allow gradual straightening and relaxing of fibers of a filter material being cleaned by the apparatus and allow relatively clean fluid to pass through the filter material in a reverse direction upon application of a suction pressure in the internal cavity, and allow the relatively clean fluid and solids previously adhered to the fibers to enter the open ended chambers, then the slots and then the internal cavity while substantially preventing other relatively less clean fluids and solids from entering the open-ended chambers, slots and internal cavity, the first and second hoods each consisting of first and second cylindrical rods extending substantially parallel to their respective slot and attached to the tubular body.
 21. An apparatus for treating water or wastewater comprising: a vessel having a floor and walls defining a cloth filter zone comprising one or more cloth filter cassettes positioned vertically therein, and one or more backwash headers positioned adjacent one main filter surface of at least one cloth filter cassette; wherein the backwash header comprises a tubular body having a length, a diameter, first and second ends, a longitudinal axis, and an exterior surface, the tubular body defining at least one internal cavity; the body comprising at least one suction slot sized to allow fluids and solids to enter the cavity from outside of the exterior surface, and a hood structure attached to a portion of the exterior surface of the body proximate to and on opposite sides of the slot, extending away from the suction slot to form an open-ended chamber, the open-ended chamber comprising first and second open-ended sub-chambers on opposites sides of the slot, wherein the open-ended sub-chambers have sufficient volume to allow gradual straightening and relaxing of fibers of a filter material being cleaned by the backwash header, and allow relatively clean fluid to pass through the filter material in a reverse direction upon application of a suction pressure in the internal cavity, and allow the relatively clean fluid and solids previously adhered to the fibers to enter the open-ended chamber, then the slot and internal cavity while substantially preventing other relatively less clean fluids and solids from entering the open-ended chamber, slot and cavity, the first and second hoods each consisting of first and second cylindrical rods extending substantially parallel to their respective slot and attached to the tubular body.
 22. The apparatus of claim 21 wherein one or more of the backwash headers comprises first and second suction slots positioned on substantially opposite exterior surface portions of the tubular body, wherein each suction slot is substantially parallel to the longitudinal axis of the tubular body, each suction slot has a length that is less than the length of the tubular body, the first and second suction slots positioned away from the first and second ends of the tubular body, the first and second suction slots sized to allow fluids and solids to enter the cavity from outside of the exterior surface; the hood structure comprises first and second hoods attached to separate portions of the exterior surface of the tubular body and extending away from the respective first and second suction slots to form first and second open-ended chambers defined by the respective hoods and portions of the exterior surface near respective suction slots, the first and second open-ended chambers each comprising respective first and second open-ended sub-chambers on opposites sides of their respective slot, wherein the open-ended sub-chambers have sufficient volume to allow gradual straightening and relaxing of fibers of a filter material being cleaned by the backwash header.
 23. A method of treating water or wastewater comprising: flowing a suspended solids stream into a cloth filter vessel, the cloth filter vessel comprising a cloth filter zone comprising at least one cloth filter media cassette, producing a filter cake on external surfaces of the cloth filter media and a treated effluent stream from each cassette, and backwashing the cloth filter media using a backwash header, the backwash header comprising: a body having a length, first and second ends, a longitudinal axis, and an exterior surface, the body defining at least one internal cavity; the body comprising at least one slot sized to allow fluids and solids to enter the internal cavity from outside of the exterior surface; and a structure attached to the exterior surface of the body proximate to and on opposite sides of the slot, the structure substantially parallel to and extending away from the slot to form an open-ended chamber, the open-ended chamber comprising first and second open-ended sub-chambers on opposites sides of the slot, the first and second open-ended sub-chambers each consisting of first and second cylindrical rods extending substantially parallel to their respective slot and attached to the tubular body; wherein the open-ended sub-chambers have sufficient volume to allow gradual straightening and relaxing of fibers of a filter material being cleaned by the apparatus, and allow relatively clean fluid to pass through the filter material in a reverse direction upon application of a suction pressure in the internal cavity, and allow the relatively clean fluid and solids previously adhered to the fibers to enter the open-ended chamber, then the slot and internal cavity while substantially preventing other relatively less clean fluids and solids from entering the open-ended chamber, slot and internal cavity.
 24. The method of claim 23 wherein the cloth filter media is selected from the group consisting of needled nonwoven polyamide filter media, acrylic cloth, polyester cloth, nylon fibers, other carpet-like materials, and combinations thereof.
 25. The method of claim 23 wherein the suspended solids stream is a chemically-induced flocculated stream.
 26. The method of claim 23 comprising monitoring a fluid level in the vessel and starting backwashing upon reaching a setpoint level in the vessel.
 27. The method of claim 26 wherein filtration is continuous during backwashing.
 28. The method of claim 23 comprising moving the backwash header in a first direction across a surface of the cloth filter media during a first period of time, and reversing the direction of movement of the backwash header to move across the same surface of the cloth filter media during a second period of time.
 29. The method of claim 23 wherein the backwashing occurs periodically. 